At present, quaternized dialkylaminoalkylene (meth)acrylates are used as papermaking additives such as most of retention aids, drainage aids for paper boards, paper strengthening agents, and coagulants for pretreatment of papermaking stock. The reason that the above materials are most widely used may be that their cost is reasonable and they are easy to produce. However, it is known that a polyvinylamine exhibits excellent effects as a pitch controlling agent used to prevent a pitch trouble caused by an adhesive pitch. A polyvinylamine is effective also as a drainage aid for paper boards because the improvement in dewaterability during press dewatering is higher than that when the above-described acrylic-based macromolecules are used. When a polyvinylamine is used as a coagulant for dewatering of sludge, the water content of dewatered cake is reduced specifically in some cases, and it is therefore understood that it is important to use the acrylic-based macromolecules and polyvinylamine for different purposes. It is suggested that the above phenomena be due to the primary or secondary amino groups in the polyvinylamine macromolecules.
A polyvinylamine is a primary amino group-containing vinyl polymer having the simplest structure and methods such as a method in which poly-N-vinylcarboxylic acid amide is hydrolyzed with an acid or a base, a method in which poly-N-vinyl-O-t-butylcarbamate is hydrolyzed, or a method in which the Hofmann reaction of polyacrylamide is performed in the presence of a hypohalous acid and an alkali metal hydroxide are known.
In the method in which a polymer of an N-vinylcarboxylic acid amide monomer is hydrolyzed with an acid or a base, the monomer used as the raw material can be easily synthesized. In addition, a polymer with a high molecular weight can be relatively easily obtained by hydrolysis of a radical polymerization reaction product of N-vinylcarboxylic acid amide, and the method is highly safe. Therefore, this method is useful as an industrial production method.
However, an aqueous solution of a high-molecular weight polyvinylamine has high viscosity and is therefore difficult to handle. In order to utilize a high-concentration polyvinylamine, it is preferable to use the polyvinylamine in the form of a water-in-oil emulsion.
Disclosed is a method of mechanically emulsifying an aqueous solution of the polyvinylamine in the presence of an emulsifier to produce as a water-in-oil emulsion of a polyvinylamine. The viscosity of the aqueous solution of a high-molecular weight polyvinylamine is high. Therefore, in this method, the concentration of the aqueous polyvinylamine solution must be reduced to a level at which emulsification can be achieved. This method is not suitable for the purpose of utilizing a high-concentration polyvinylamine (Patent Literature 1).
One useful method of producing a water-in-oil emulsion of a polyvinylamine is to produce a water-in-oil emulsion of poly-N-vinylcarboxylic acid amide and then to hydrolyze the water-in-oil emulsion with an acid or a base.
Patent Literature 2 discloses a method of producing a water-in-oil emulsion of poly-N-vinylcarboxylic acid amide. However, in this production method, there is no description about a water-in-oil emulsion of a polyvinylamine that is obtained by hydrolysis of the above water-in-oil emulsion.
Patent Literature 3 discloses a method of hydrolyzing a water-in-oil emulsion of a copolymer of N-vinylformamide and acrylonitrile with an acid. In this method, it is necessary to use acrylonitrile as a monomer, and it is also necessary to perform hydrolysis with an acid. An ester bond in an emulsifier used for acid hydrolysis is easily cleaved by the acid. In this method, since a base cannot be used for neutralization, the stability of the emulsion is low.
Patent Literature 4 discloses a method of producing a stable water-in-oil emulsion of a polymer obtained by hydrolysis of N-vinylcarboxylic acid amide with an acid or a base in the presence of a mixture of specific emulsifiers. Also in this production method, an emulsifier having an ester bond is used, and the stability of the emulsion is low since the ester bond is easily cleaved with an acid or a base.
Patent Literature 5 discloses that, when a water-in-oil emulsion of a polymer of N-vinylamide is hydrolyzed by an acid or an alkali, an antioxidant, a reducing agent, or an aldehyde capture agent in an amount of 0.01 to 20% by mass with respect to the polymer is added to the w/o-polymer emulsion before, during, or after hydrolysis, for the purpose of improving the stability of the emulsion after the hydrolysis. In addition, there is a description that the polymerization may be performed in the presence of an emulsifier having an HLB of 9 to 20 and produced by synthesizing a reaction product of a glycidyl ether of a C10 to C22 aliphatic alcohol and a polyhydric alcohol and then reacting a C2 to C4 alkylene oxide with the reaction product.
As described above, there is no conventional method that can produce a stable water-in-oil emulsion of a polyvinylamine that is obtained by hydrolyzing a water-in-oil emulsion of poly-N-vinylcarboxylic acid amide with an acid or a base.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2004-59747
Patent Literature 2: European Patent Application Laid-Open No. 0231901
Patent Literature 3: Japanese Patent Application Laid-Open No. Hei. 05-309208
Patent Literature 4: Japanese Translation of PCT International Application Publication No. Hei. 10-500714
Patent Literature 5: Japanese Patent Application Laid-Open No. Hei. 05-117313